1. Field of the Invention
The present invention provides compounds having estrogenic activity. More specifically, the compounds of the present invention are isolated from plants.
2. The Prior Arts
Through the period of menopause, menopausal women may suffer from symptoms like hot flashes, night sweats, and palpitation, etc. To relieve these symptoms, the menopausal women are usually recommended to be treated by hormone replacement therapy (HRT). However, previous studies indicate that administering estrogen alone for therapy may increase the risk of endometrial cancer. To minimize this deleterious effect caused by HRT, the co-administration of estrogens (e.g. 0.625 mg/day conjugated equine estrogens, CEE) along with progestin (e.g. 2.5 mg/day medroxyprogesterone acetate, MPA) is employed so as to reduce the increasing risk of endometrial cancer. On the other hand, in July 2002, the Women's Health Initiative (WHI) of USA reported that the continuous treatment by HRT for more than five years would lead to a higher risk of breast cancer, heart attacks, strokes, and pulmonary embolism. However, the therapy did reduce the women's risk of developing hip fractures and colorectal cancer.
Further, to compensate for losing the ability to secrete estrogen, providing menopausal women with estrogen is highly desirable for the prevention of menopausal symptoms and for the increase of risk of heart attacks and osteoporosis.
Conventional molecular biological studies have indicated that estrogen exerts its effect by binding to estrogen receptors and activate the expression of genes modulated by the estrogen, wherein the promoter of these genes comprising a sequence of estrogen responsive element (ERE). A compound that binds to an estrogen receptor and produces only partial effects is called a partial agonist, such as diethylstilbestrol (DES). A compound that binds to an estrogen receptor and does not produce any effect is called an antagonist or an anti-estrogen, such as tamoxifen, utilizing for inhibiting estrogen-dependent cancers. To date, two estrogen receptors, ERα and ERβ, have been identified. The distributions of these two receptors varied in different tissues. Accordingly, future investigation for treating the menopausal women might focus on a class of molecules called selective estrogen receptor modulators (SERM), which could stimulate estrogen receptors in the cells of blood vessels and bone tissues while bypassing other estrogen receptors in the cells of breast and ovarian, and benefit the numerous menopausal women.
Owing to the foregoing drawbacks exerted by conventional estrogens (e.g. CEE) isolated from animals, it is advantageous to develop a novel compound as a substitute thereof.